Device for operating a windshield wiper

ABSTRACT

A arrangement for operating a windshield wiper in a direct mode, an intermittent mode or a continuous mode, having a sensor device for detecting a degree of moisture on the windshield, an evaluation device for the sensor signal and an actuation unit for the windshield wiper. A non-disturbing smoothing of the interval times is accomplished in a simple manner in that an interval time control has a smoothing stage for the interval time with which it can be determined during which time segment of predetermined time segments within the interval time a wetting event occurs, starting from the beginning of the interval, and with which the second interval time can be shortened all the more, the earlier the time segment appears during which the wetting event occurs.

This application is a 371 of PCT/DE 96/00668 filed Apr. 17, 1996.

BACKGROUND OF THE INVENTION

The invention relates to an arrangement for operating a windshield wiperin either a direct mode, wherein, in the event of a wetting event on thewindshield, a wiping action is triggered directly, in an intermittentmode wherein, in the event of a corresponding wetting event, a sequenceof wiping actions with a predeterminable interval time is triggered, orin a continuous mode, wherein wiping actions follow one another withouta break, with the arrangement having a sensor device for detecting thedegree of moisture on the windshield and for emitting a sensor signal,having an evaluation device receiving the sensor signal, whichevaluation device is provided with a moisture-detecting stage, aninterval time control and a control signal generating device, and havingan actuation unit for the windshield wiper which can be actuated by theevaluation device to produce the wiping actions.

An arrangement of this type has been revealed as being known in DE 40 18903 C2. In this known arrangement, the wiping operation is controlled onthe basis of a sensor signal of a sensor device, which signal isevaluated by an evaluation device. An intermittent mode is providedwherein the intervals can be selected, on the one hand, as a function ofwetting events including rain or another moisture coating on thewindshield and as a function of preceding interval times and of theduration of triggered wiping actions. During this process, unfavorable,abrupt changes of the interval times may occur.

SUMMARY AND ADVANTAGES OF THE INVENTION

It is the object of the invention to provide an arrangement of the typementioned at the outset, wherein a smoothing of the interval times isaccomplished in a simple manner.

This object generally is achieved by an arrangement for operating awindshield wiper in either a direct mode wherein a wiping action istriggered directly in the event of a wetting event on the windshield, inan intermittent mode wherein a sequence of wiping actions with apredeterminable interval time is triggered in the event of acorresponding wetting event, or in a continuous mode wherein wipingactions follow one another without a break, with the arrangement havinga sensor device for detecting the degree of moisture on the windshieldand for emitting a sensor signal, having an evaluation device receivingthe sensor signal, which evaluation device is provided with amoisture-detecting stage, an interval time control and a control signalgenerating device, and having an actuation unit for the windshield wiperwhich can be actuated by the evaluation device to produce the wipingactions; and wherein the interval time control has a smoothing stage forthe interval time (t_(I), t_(I+1)) with which it can be determinedduring which time segment of predetermined time segments within a firstinterval time (t_(I)) a wetting event occurs, starting from thebeginning of the interval and with which the second interval time(t_(I+1)) can be shortened all the more, the earlier the time segmentappears during which the wetting event occurs.

Accordingly, it is provided that the interval time control has asmoothing stage for the interval time with which it can be determinedduring which time segment of predetermined time segments within theinterval time a wetting event occurs, starting from the beginning of theinterval, and with which the second interval time can be shortened allthe more, the earlier the time segment appears during which the wettingevent occurs.

In this manner, great, abrupt changes of the interval times duringsuccessive wiping actions, which might disturb a driver, can beprevented.

A simple measure for attaining a good smoothing of the interval times isthat the interval time is divided into two time segments of identicalsize, and that the second interval time remains the same as the old oneif the wetting event occurs during the second time segment and isreduced by a fixed portion of the old interval time if the wetting eventoccurs during the first time segment.

Furthermore, disturbing, abrupt changes of the interval time areprevented if it is provided that the interval time of a third intervaltime, which then follows the second interval time, is shortened by agreater percentage portion than the second interval time if a wettingevent occurs during the first time segment of the second interval timeand that further interval times are shortened by the same percentageportion as the third interval time if wetting events occur during thefirst time segment of the respectively preceding interval times.

A further simple measure to improve the smoothing is that the secondinterval time remains constant if a wetting event occurs outside of thefirst interval time, that the third interval time is extended by apredetermined percentage portion if a wetting event occurs outside ofthe third interval time, that a fourth interval time is extended by agreater percentage portion than the third interval time if a wettingevent occurs outside of the third interval time, and that switching tothe direct mode occurs if a wetting event occurs outside of the fourthinterval time.

A feature of the arrangement which provides that switching to the directmode can only take place if, after a last interval time, a furtherinterval time has passed, prevents that a double wiping occurs duringthe transition from the intermittent mode to the direct mode.

A further advantageous measure to improve the smoothing of the intervaltimes is attained by the feature of the arrangement which provides thatthe first time segment is again divided into two time ranges ofidentical size and that the percentage portion of the shortening of thesubsequent interval time is greater if the wetting event occurs duringthe first time range than if it occurs during the second time range.

In order to clearly define the intermittent mode, it is further providedthat the interval times range within a minimum and a maximum limit andthat switching takes place to the continuous mode if the minimum limitis not reached and to the direct mode if the maximum limit is exceeded.

A transition to the intermittent mode is attained in a simple andreliable manner in that the intermittent mode can only be reached fromthe direct mode and that the first interval time is determined from themean value of the two preceding break times of the direct mode if noneof the two times is longer than the maximum limit of the interval time.

The invention is described below in greater detail by way of anembodiment with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block illustration of an arrangement for operatinga windshield wiper,

FIG. 2 is an illustration of interval times to explain the operatingmode of the arrangement, and

FIG. 3 shows the essential segments of an evaluation device shown inFIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates an arrangement for operating a windshield wiperhaving a sensor device 10 emitting a sensor signal S, which may alreadybe preprocessed, to an evaluation device 20. The evaluation device 20generates a control signal ST by means of which a suitable wipingoperation in accordance with the evaluation of the sensor signal S canbe triggered via an actuation unit 30.

Normally, there are provided for such an arrangement a direct mode,wherein wiping operations are triggered, if necessary, in the event ofoccasional wetting events such as rain, snow or wet dirt; usually thereare wiping breaks of different lengths in between the wiping actions.For other wetting events such as drizzle or if the windshield closes updue to fine rain drops during fog, an intermittent mode is triggered,whereas, for example, for normal rain, a continuous mode (without wipingbreaks) is switched on.

During the intermittent mode, different interval times t_(I+1) etc. canbe selected within a minimum interval time and a maximum interval timeby way of the evaluation device 20 as a function of the wetting event.Abrupt changes of the interval times can have a disturbing effect on thedriver. Here, according to FIGS. 2 and 3, a smoothing is initiated whenthe interval times change.

For this purpose, according to FIG. 2, an interval time t_(I) between abeginning of an interval IB and an end of an interval IE is subdividedinto two time segments of identical size. The first time segment canfurther be subdivided into two time ranges of identical size, as isshown in FIG. 2. FIG. 3 shows the essential evaluation stages of theevaluation device 20 in a block diagram.

If a wetting event, which is detected by a detector stage 21, occursduring the second time segment, the then following second interval timeT_(I+1) remains unchanged with respect to the old first interval timet_(I). If a wetting event occurs during the second time range of thefirst time segment, the second interval time t_(I+1) is extended by 25%with respect to the first interval time t_(I), whereas the secondinterval time t_(I+1) is extended by 50% if the wetting event occursduring the first time range of the first time segment. By means of aninterval time control 22, an information is correspondingly released toa control signal generating device 23.

Furthermore, the interval time control 22 may be configured such thatafter an initial shortening of the interval time, an immediatelyfollowing further shortening is more pronounced if a wetting eventoccurs during the same time range. If, for example, the second intervaltime t_(I+1) is shortened by 25% because a wetting event occurs duringthe second time range of the first time segment, a third interval timeis shortened, for example, by 50%, if a wetting event occurs during thesecond time range of the first time segment of the second interval timet_(I+1). Each further interval time is shortened with respect to thepreceding time interval by a further 50% in the event of a wetting eventduring the respective time range.

If a wetting event occurs, for example, outside of the first intervaltime t_(I), the duration of the subsequent second interval time t_(I+1),for example, remains unchanged, whereas in the event of a subsequentextension, the third interval time is extended with respect to thesecond one, for example, by 25%, and in the event of a third extension,the fourth interval time is extended by 50% compared to the third one.In the event of a further extension, switching to the direct modepreferably takes place.

Due to the direct response of the direct mode to a wetting event--atransition to a direct mode might, unfavorably, immediately triggeranother wiping action when a wetting event occurs after a last wipingaction in the intermittent mode; it is therefore provided that switchingto the direct mode can only take place following a further intervaltime.

As was already mentioned, the intermittent mode can only be reached fromthe direct mode. The first interval time is then calculated from themean value of the last two break times of the direct mode, with atransition to the intermittent mode taking place if the two times arenot longer than the maximum interval time.

A smoothened intermittent mode can be accomplished in a simple mannerwith the above-described measures, while it is possible, however, toadapt the wiping operation quickly enough to changing wettingsituations.

Preferably, the evaluation device 20 has a digital design and maycomprise the individual stages in a program so as to implement themeasures described.

We claim:
 1. An arrangement for operating a windshield wiper in either adirect mode wherein, in the event of a wetting event on the windshield,a wiping action is triggered directly, in an intermittent mode wherein,in the event of a corresponding wetting event, a sequence of wipingactions with a predeterminable interval time is triggered, or in acontinuous mode wherein wiping actions follow one another without abreak, the arrangement having: a sensor device for detecting the degreeof moisture on the windshield and for emitting a sensor signal; anevaluation device receiving the sensor signal, which evaluation deviceis provided with a moisture-detecting stage, an interval time controlfor operation in the intermittent mode and a control signal generatingdevice; and an actuation unit for the windshield wiper which can beactuated by the evaluation device to produce the wiping actions, andwherein: the interval time control includes smoothing stage means forconsidering the interval time (t_(I), t_(I+1)) and for determiningduring which time segment of predetermined time segments within a firstinterval time (t_(I)) a wetting event occurs, starting from thebeginning of the interval (IB), and for shortening a second followinginterval time (t_(I+1)) the earlier the time segment appears duringwhich the wetting event occurs during the first time interval.
 2. Anarrangement according to claim 1, wherein: each interval time (t_(I)) isdivided into two time segments of identical size; and the interval timecontrol causes the second interval time (t_(I+1)) to remain the same asthe preceding first interval time if the wetting event occurs during thesecond time segment of the first interval time and to be reduced by afixed portion of the first interval time (t_(I)) if the wetting eventoccurs during the first time segment of the first interval time.
 3. Anarrangement according to claim 1, wherein the smoothing stage meanscauses the interval time of a third interval time, which then followsthe second interval time (t_(I+1)), to be shortened by a greaterpercentage portion than the second interval time (t_(I+1)) if a wettingevent occurs during the first time segment of the second interval time(t_(I+1)), and shortens further interval times by the same percentageportion as the third interval time if wetting events occur during thefirst time segment of the respectively preceding interval times.
 4. Anarrangement according to claim 1 wherein said smoothing stage meanscauses the second interval time (t_(I+1)) to remain constant if awetting event occurs outside of the first interval time, a thirdinterval time to be extended by a predetermined percentage portion if awetting event occurs outside of the third interval time, that a fourthinterval time is extended by a greater percentage portion than the thirdinterval time if a wetting event occurs outside of the third intervaltime, and switching to the direct mode occurs if a wetting event occursoutside of the fourth interval time.
 5. An arrangement according toclaim 4 wherein switching to the direct mode can only take place if,after a last interval time, a further interval time has passed.
 6. Anarrangement according to claim 2 wherein: the first time segment isagain divided into first and second time ranges of identical size; andsaid smoothing means causes the percentage portion of the shortening ofthe subsequent interval time to be greater if the wetting event occursduring the first time range than if it occurs during the second timerange of the first time segment.
 7. An arrangement according to claim 1,wherein: the interval times range within a minimum and a maximum limit;and said interval time control causes switching to take place to thecontinuous mode if the minimum limit is not reached and to the directmode if the maximum limit is exceeded.
 8. An arrangement according toclaim 7, wherein the intermittent mode can only be reached from thedirect mode; the interval time control determines the first intervaltime (t_(I)) from the mean value of the two preceding break times of thedirect mode if none of the two times is longer than the maximum limit ofthe interval time.
 9. A method for operating a windshield wiper eitherin a direct mode wherein a wiping action is triggered. directly in theevent of a wetting event on the windshield, in an intermittent modewherein a sequence of wiping actions with a predeterminable intervaltime is triggered in the event of a corresponding wetting event, or in acontinuous mode wherein wiping actions follow one another without abreak, said method comprising: detecting the degree of moisture on thewindshield and emitting a sensor signal; evaluating the sensor signal todetermine the desired mode of wiping action, including controlling timeintervals during the intermittent mode; and activating the windshieldwipers to produce the desired wiping actions; and wherein thecontrolling of the time intervals includes: determining during whichtime segment of predetermined time segments within a first interval time(t_(I)) a wetting event occurs starting from the beginning of theinterval (IB), and shortening a second interval time (t_(I+1)) all themore, the earlier the time segment appears during which the wettingevent occurs.
 10. The method according to claim 9, further including:dividing each interval time (t_(I)) into first and second time segmentsof identical size; and causing the second interval time (t_(I+1)) toremain the same as the first interval time if the wetting event occursduring the second time segment, and reducing the second interval time bya fixed portion of the first interval time (t_(I)) if the wetting eventoccurs during the first time segment.
 11. The method according to claim9 further comprising: shortening the interval time of a third intervaltime, which follows the second interval time (t_(I+1)), by a greaterpercentage portion than the second interval time (t_(I+1)) if a wettingevent occurs during the first time segment of the second interval time(t_(I+1)); and shortening further interval times by the same percentageportion as the third interval time if wetting events occur during thefirst time segment of the respectively preceding interval times.
 12. Themethod according to claim 11 further comprising: causing the secondinterval time (t_(I+1)) to remain constant if a wetting event occursoutside of the first interval time; extending the third interval time bya predetermined percentage portion if a wetting event occurs outside ofthe third interval time; extending a fourth interval time by a greaterpercentage portion than the third interval time if a wetting eventoccurs outside of the third interval time: and, switching to the directmode if a wetting event occurs outside of the fourth interval time. 13.The method according to claim 12, wherein switching to the direct modetakes place only if, after a last interval time, a further interval timehas passed.
 14. The method according to claim 10, further comprising:dividing the first time segment into first and second time ranges ofidentical size, and, causing the percentage portion of the shortening ofthe subsequent interval time to be greater if the wetting event occursduring the first time range than if it occurs during the second timerange of the firs time segment.
 15. The method according to claim 14,wherein: the first and second interval times range within a minimum anda maximum limit; and, switching to the continuous mode takes place ifthe minimum limit is not reached and switching to the direct mode takeplace if the maximum limit is exceeded.
 16. The method according toclaim 15, wherein switching to the intermittent mode can only be reachedfrom the direct mode: and further including determining the firstinterval time (t_(I)) from the mean value of two preceding break timesof the direct mode if none of the two times is longer than the maximumlimit of the interval time.